Emily-Anne Patt, James Stockton
In Noisy Judgments: A probability surface-based analysis of umpiring variability, we establish the size, shape, and position of the strike zone as called during an MLB game by building a prior probability surface from 5.3 million called balls and strikes between the 2008 and 2022 seasons. We used this surface to evaluate changes in the actual strike zone over time, stress-testing the reliability of the model with established baseball facts related to batter and pitcher handedness and seasonal shifts. A sensitivity study shows the validity of the surface at lower pitch counts, allowing us to evaluate individual player and umpire performance across games and within a game. This analysis leads us to propose a novel methodology for evaluating a catcher's framing ability--the Framing Induced Strike Zone (FISZ).